Why Hurricane Floods Can Cause EV Battery Fires

In the wake of Hurricane Helene, authorities are warning EV owners that batteries and salt water are a bad combination.

Tesla Fire after Hurricane Helene

Photo by: Pinellas County Government

Mack Hogan

By: Mack Hogan

Sep 30, 2024 at 4:30pm ET

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Floods have pummeled the Southeast, especially North Carolina, destroying countless structures and leaving many vehicles at least partially underwater.
Authorities say electric car batteries that have been submerged in salt water pose a fire risk, as the flooding can trigger a short circuit.
If your vehicle has been flooded, be aware of the low but real chance that it can ignite, and never try to drive any vehicle after it has been flooded without first getting it checked out by a technician.

As the Southeastern U.S. is reeling in the wake of Hurricane Helene, authorities are reminding EV owners to be careful if their vehicles have been flooded, as the Associated Press reported. We've even seen video evidence of an allegedly flood-damaged Tesla Model X exploding in a garage.

Tesla has long warned of the fire risk that flooded cars pose. The company recommends not driving a car that has been submerged until it is inspected by an authorized repair facility, and says that flooded vehicles should be parked 50 feet from any structure. Florida Governor Ron DeSantis urged EV owners to get their vehicles to higher ground ahead of the storm. Tom Barth, chief of the special investigations branch of the National Transportation Safety Board's office of highway safety, told The Associated Press that saltwater can short-circuit batteries. The conductive salt water can bridge the gap between the battery's positive and negative terminals, shorting the pack and leading to thermal runaway.

Batteries are designed to be safe in a very of conditions, including submersion, so most have seals to prevent any moisture from getting in. But salt water is extraordinarily corrosive—look at the undercarriage of any car driven somewhere where they salt the roads—and those seals can fail.

“Where it begins to be a problem is if you have the batteries submerged in standing water. That’s where it starts to overcome the moisture seals in the battery,” Barth told the AP.

That doesn't mean this is likely to happen. According to National Highway Traffic Safety Administration research, also cited by the AP, after Hurricane Ian flooded 3,000-5,000 electric vehicles. Six hundred were declared total losses and 36 of those caught fire. That means roughly one-tenth of 1% of flooded EVs overall caught fire, but about 6% of those that were totaled did ignite. Research at the Idaho National Laboratory—conducted as part of the NHTSA study—found various ways in which water from Hurricane Ian penetrated the battery packs of flooded cars:

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Their sample included a Lucid Air, Porsche Taycan, Tesla Model X, Model S, Model Y and Model 3. None of them seemed to pose a fire risk, but researchers were clear that it's possible for EVs to ignite after submersions. Experts also note that a fire can sometimes start after the floodwater has receded, so just because it's dry now doesn't mean it's safe. Like any car, you shouldn't try to use it after a flood before getting it checked out. Even if there's no fire risk, attempting to turn it on may cause further damage. And regardless of your vehicle's powertrain, if the floodwater went past the floorboards you are likely looking at a total loss.

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But if you're in North Carolina right now, you can't exactly call a tow truck. If you have an EV that is or was submerged—especially if it is inside of an attached garage—be aware that it is a potential fire risk. Given that emergency services may struggle to reach a house quickly, it may be safest to move to a safer location. If you cannot safely move, stay aware of the risk while also understanding that a fire is extremely unlikely.

As EVs evolve, automakers are also working hard to make sure they fail safely when flooded or in extreme circumstances. Authorities, automakers and regulators continue to learn more about how to handle EV-related fires and specific issues, and EV fires remain far rarer than internal combustion fires. EVs with Vehicle-to-Load (V2L) or Vehicle-to-Home (V2H) functions can also be lifesavers during natural disasters, allowing owners to power fridges, lights and other home electronics when the grid is down. But if you know you're in a flood zone, the safest thing to do is move your vehicle out of the danger zone before the water rises.